This disclosure relates generally to drive-by-wire steering systems. More specifically, this disclosure relates to drive-by-wire steering systems having a stop mechanism.
Vehicles require a steering system to control the direction of travel. Previously, mechanical steering systems have been used. Mechanical steering systems typically include a mechanical linkage or a mechanical connection between the steering wheel and the vehicle""s road wheels. Thus, movement of the steering wheel causes a corresponding movement of the road wheels. Movement of such mechanical systems is often power assisted through the use of hydraulic assists or electric motors.
Mechanical steering systems are being replaced and/or supplemented by electrically driven steering systems, commonly known as xe2x80x9csteer-by-wirexe2x80x9d systems. Such steer-by-wire systems to varying extents replace, for example, the mechanical linkage between the steering wheel and the vehicle wheels with an electrically assisted actuator.
This migration to steer-by-wire systems is being made to improve fuel economy, increase vehicle modularity, reduce load on the engine of the vehicle, reduce vehicle weight, and provide four-wheel-steering. For example, the use of steer-by-wire systems eliminates the need for hydraulic fluids, provides a tighter turning radius, and reduces the weight of the vehicle.
Additionally, steer-by-wire systems eliminate various undesirable problems present in mechanical systems. For example in steer-by-wire systems, the steering wheel is mechanically isolated from the road wheels. Thus, excessive deleterious feed back to the steering wheel in the form of shudders, and steering wheel kickback from the road wheels is eliminated.
Unfortunately, mechanically isolating the steering wheel from the road wheel also eliminates desired feed back. For example, during the use of mechanical steering systems, the rotation of the steering wheel is mechanically limited by the travel of the road wheels of the vehicle. Unfortunately, the mechanical isolation provided by drive-by-wire steering systems eliminates this desired feedback.
A drive-by wire steering system is provided. The steering system comprises a steering shaft and a stop mechanism. The steering shaft is configured for a first angular displacement about a first axis. The steering shaft comprises a first geared portion and a first end. The first end is connectable to a vehicle""s steering wheel. The stop mechanism comprises a stop portion and a second geared portion. The stop portion defines a first position and a second position. The first geared portion and the second geared portion are operatively engaged such that angular displacement of the steering shaft imparts a second angular displacement about a second axis to the stop mechanism. The first angular displacement is limited when the second angular displacement is such that the steering shaft abuts the stop portion at either the first position or the second position.
A method is provided for protecting a sensor in a drive-by wire steering system where the sensor has a predetermined displacement range. The method includes connecting the sensor to a steering shaft, engaging a stop mechanism to the steering shaft, and abutting the stop mechanism and the steering shaft at a first position and a second position to limit the angular displacement of the steering shaft such that the sensor is maintained within the predetermined displacement range. The steering shaft is configured for a first angular displacement about a first axis. The stop mechanism is engaged to the steering shaft such that the first angular displacement imparts a second angular displacement about a second axis to the stop mechanism. The first angular displacement is greater than the second angular displacement.
A method is provided for improving the driveability of a drive-by wire steering system. The method includes engaging a stop mechanism and a steering shaft such that a first angular displacement of the steering shaft about a first axis imparts a second angular displacement about a second axis to the stop mechanism. The first angular displacement is greater than the second angular displacement. The method also includes limiting the first angular displacement by an interference of the stop mechanism with the steering shaft at a first position and a second position such that a range of motion is provided to the drive-by wire steering system that mimics a mechanically linked steering system range of motion.